                The following references describe neutrophil elastase inhibitors with a monocyclic dihydro-pyrimidinone core: GB2392910, WO04024700, WO05082864, WO05082863, DE102006031314, U.S. Ser. No. 10/001,0024, WO10115548, WO09080199, DE102007061766, WO06136857, WO06082412, WO12002502.        The following references describe neutrophil elastase inhibitors with a bicyclic tetrahydropyrrolopyrimidinedione core: WO07129060, WO08135537, U.S. Ser. No. 09/009,3477, WO09013444, WO09060206, WO09060203, WO09060158, U.S. Ser. No. 11/003,4433.        The following references describe neutrophil elastase inhibitors with core structures other than those herein before mentioned: WO04020412, WO04020410, WO03053930, WO10078953, WO09135599, DE102009004197, WO11110858, WO11110859, WO09060158, WO09037413, WO04024701, U.S. Ser. No. 13/006,5913, WO13018804, WO12002502.        For a review on various inhibitors of neutrophil elastase see: P. Sjö (Future Med. Chem. 2012, 4, 651-660).        